This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Mass spectrometry-based identification and characterization of all protein complexes in a cell at a time is a long standing question. Methods are developed that allow purification, identification, and characterization of the major cellular protein complexes with both: the least bias and the highest efficiency.